Look up the number for Beretta in Maryland. Ask for the parts department and have your credit card in hand. When I bought my 5-round mags last year they were $42 each and 5$ s&h...each.
There is usually a 3-line ad in the Sako section of the Gun List (Borders, Barnes&Noble, Food Lion, gun show, etc.) offering them for $38-something IIRC. I didn't know at the time that a local gun store had them for about that price either. At least it wasn't a very expensive education.
John